Repetitive exercise devices are used to develop muscle strength and coordination through repetitive use. Such devices commonly use weights, hydraulics, fly wheels, or variable length levers to provide a resistance force when a user exercises with the device. One common repetitive exercise device includes a set of weights of equal size arranged in a vertical stack. A selector rod passes through a central aperture on each of the weights, and the selector rod is connected on the upper end to a cable which lifts the rod and any of the weights attached thereto in response to the user lifting, pushing, or pulling on an input member which is connected through various levers and pulleys to the cable. The amount of weight which is lifted by the user depends upon the number of the individual weights which are connected to the selector rod. The weights are generally in ten-pound or twenty-pound increments, and a removable pin is provided which must be manually positioned by the user to pin a selected one of the weights to the selector rod for movement with the rod. Of course, each of the weights positioned above the weight pinned to the selector rod is also lifted with the rod.
Since the individual weights typically weigh ten to twenty pounds, it is only possible to adjust the weight being lifted by the user in relatively large ten-pound or twenty-pound increments. Further, with this arrangement, the weight can only be adjusted when the weights are at rest. Thus, the same weight must be used during an entire exercise extension and return movement even though it would sometimes be desirable to lift with one force and resist return with a greater force, or even vary the weight during the course of the extension or return movement. Further, the user must typically move from the front of the device where exercise is conducted to the side or rear where the stack of weights is located so as to manually reposition the pin each time it is desired to adjust the amount of weight to be lifted. This results in undesirable interruption in the exercise program.
It will therefore be appreciated that there has been a significant need for a repetitive exercise device with an almost infinitely variable weight-loading which can be changed without the user leaving the exercise position at the front of the device. It is preferable that such a device also allow the weight-loading to be changed while the exercise is in progress, not just when the weight is at rest. Preferably, the weight-loading can also be continually adjusted during the course of the exercise so that a desirable weight-loading profile can be established for an exercise movement. Further, the preferred device will allow the weight-loading to be automatically increased and decreased during the course of an exercise program, such as by using a lower weight-loading for several lifts, and gradually increasing the weight-loading to a maximum amount, with subsequent automatic reduction of the weight-loading as programmed by the user. It is also desirable that the preferred device be constructed so that they forces experienced by the user are predictable and controlled. The present invention fulfills these needs, and further provides other related advantages.